如图:某市在“旧城改造”中计划在市内一块三角形空地上种植某种草皮来美化环境,已知这种草皮每平方米售价为a元,则购买这种草皮至少需要( )元。
构成自然景观地区差异的主要因素是( )
In my driving lesson, I learned a traffic rule that at no time _____ parked in a manner which will block emergency service.